It is well known in the art of carbonating beverages that the solubility of CO.sub.2 in liquid will increase by increasing the pressure and/or by decreasing the temperature of the mixture. The most favorable temperature conditions to achieve the so-called carbonation effect is in the temperature range between 0.degree. C and 1.degree. C. As the temperature increases, the solubility of the CO.sub.2 decreases since the gas bubbles will grow larger and leave the liquids, thus making the taste of that beverage less desirable. Hence, the desirability of subjecting and maintaining the liquid at low temperatures is evident.
One typical prior art approach involves providing a container for mixing the mixture of carbonating gas and liquid and another separate container for cooling the mixture. Such pre-cooling arrangements utilize pipes to transport the cooled liquid to the carbonation chamber which result in unavoidable thermal energy losses. This loss in cooling energy means that it is very difficult and very expensive to maintain the liquid at temperatures in the region between 0-1.degree. C for the entire piping system of the pre-cooling arrangement, and, in fact, virtually impossible to continuously maintain such a temperature range.
Another problem inherent in such pre-cooling systems which require separate containers is that the pipes are rather prone to clogging due to ice blockage.
Evaporator plates or tubes are generally used in such pre-cooling arrangements and form ice having thicknesses on the order of 10 millimeters in order to store great quantities of cooling energy. Ice having a high specific heat makes a very efficient storehouse or reserve for cooling energy.
It is known that, in nature, an ice layer having a low conductivity to differences in temperature will protect certain flowers and animals from the deleterious effects of the cold. The thicker the ice layer is, the more cooling energy can be retained, and the better the ice layer is at isolating the things to be protected from the effects of the cold.
In the art under discussion, such thick ice layers therefore do not interchange cooling energy with liquid, such as tap water having a relatively warmer temperature than the ice layer, quickly enough to make mass production of such carbonated beverages feasible and economical. Hence, the temperature in the carbonation devices of the prior art invariably rises and continuously worsens the so-called carbonation effect.
Moreover, the increase in temperature of the prior art devices not only negatively influences the carbonation effect, but also produces a relatively warmer beverage. Since the preferred temperature of such drinks is cold, it will be seen that such beverages are not desired if one quickly taps the beverage from the mixing container.
Other prior art approaches involve pressurizing the liquid during its mixing with the gas, pressurizing the beverage during transportation, and maintaining the pressurizing condition at the point of distribution, e.g. in a soda-vending mahine. Using such pressure techniques, a high amount of the carbonic acid -- which gives the beverage its flavor -- will be lost because of the foam produced.